This invention relates to the incorporation of finely divided functional solids into normally solid olefin polymers.
In the production of olefin polymer articles containing solid additives such as pigments, extenders, dies and fillers, it has been the practice in the art to combine such an additive in finely divided form with pre-extruded pellets or granules of olefin polymers in an extrusion or similar melt blending operation. In order to achieve the desired degree of uniformity of dispersion of the finely divided solid throughout the olefin polymer, it is generally necessary to reextrude or reblend the above combination a number of times. Attempts to eliminate the need for reblending and to eliminate dusting problems caused by the finely divided solid have often involved the use of premixing techniques wherein the functional solid is first combined with a polymeric carrier to form a concentrate and subsequently blended with the desired olefin polymer.
Unfortunately, copolymers that perform suitably as carriers for polymers of aliphatic olefins are generally not sufficiently compatible with polystyrene and other polymers of aromatic olefins to be suitably employed as carriers. The result of such incompatibility is delamination occurring at interfaces between the carrier of the concentrate and the polymer being pigmented which causes a loss of physical strength. In order to avoid such problems, it has been necessary to prepare concentrates having different polymers as carriers for each different polymer to be pigmented.
As would be expected, a single color concentrate, a so-called universal concentrate, that could be suitably combined with any olefin polymer whether it be aliphatic or aromatic is highly desirable.